Question

The velocity of a body of mass$20kg$ decreases from$20m/s$ to $5m/s$ in a distance of $100m$. Force on the body is

• A. –27.5 N
• B. –47.5 N
• C. –37.5 N
• D. –67.5 N

Answer 1

The correct option is C

–37.5 N

Explanation for correct answer:-

Option (C):

Step 1. Given data:

$velocity\left(v\right)=5m/s$

$Initialvelocity\left(u\right)=20m/s$

$speed\left(S\right)=100m$

Step 2. Formula used:

$v^2=u^2+2as$

Where, $v=finalvelocity,u=initialvelocity,a=acceleration,ands=speed$

Step 3. Calculating the value of acceleration:

$\begin{array}{rcl}{v}^2& =& u^2+2as\\ {\left(5\right)}^2& =& {\left(20\right)}^2+2\times a\times 100\\ 25& =& 400+200\times a\\ a& =& -1.875m/s^2\end{array}$

Step 4. Now use the formula for force:

$$\begin{gathered} F=ma \\ where,F=force,m=mass,anda=acceleration \end{gathered}$$

Step 5. Calculate the value for force:

$\begin{array}{rcl}F& =& ma\\ & =& 20\times (-1.875)\\ & =& -37.5Newton\end{array}$

Hence, the correct answer is option (C).